Warn on missing OVERRIDE/virtual everywhere, not just in header files.

ui/views/widget/widget_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop.h"
 #include "base/utf_string_conversions.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/base/events/event_utils.h"
@@ skipping 1728 matching lines @@
   EXPECT_TRUE(delegate->on_before_init_called());
   EXPECT_TRUE(delegate->is_top_level());
 }
 
 // A scumbag View that deletes its owning widget OnMousePressed.
 class WidgetDeleterView : public View {
  public:
   WidgetDeleterView() : View() {}
 
   // Overridden from View.
-  bool OnMousePressed(const ui::MouseEvent& event) OVERRIDE {
+  virtual bool OnMousePressed(const ui::MouseEvent& event) OVERRIDE {
     delete GetWidget();
     return true;
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(WidgetDeleterView);
 };
 
 TEST_F(WidgetTest, TestWidgetDeletedInOnMousePressed) {
   Widget* widget = new Widget;
@@ skipping 10 matching lines @@
   gfx::Point click_location(45, 15);
   ui::MouseEvent press(ui::ET_MOUSE_PRESSED, click_location, click_location,
       ui::EF_LEFT_MOUSE_BUTTON);
   widget->OnMouseEvent(&press);
 
   // Yay we did not crash!
 }
 
 }  // namespace
 }  // namespace views